Memento

The reason the film memento is a thriller is because of the questions that the film makes you ask and the technique of showing the end before the beginning. By showing the outcome of the film straight away the audience is not expecting to be confused about the end, but more interested in how certain aspects come about "Why does he kill him? Who is this man?". By making the audience have to discover facts about the characters and storyline during the film makes this a thriller as a good thriller needs to grab the audiences attention straight away and not let them stop questioning until the end finally tells them what they need to know.